Clothing wire and method for producing staple fibre nonwovens

ABSTRACT

A clothing wire for mounting on a clothing roll of a carding machine has a base section ( 1 ) and a blade section ( 4 ). A gradient dh/db of the height (h) as a function of the width (b) of at least a first section ( 10 ) of at least one blade-section side face ( 5, 6 ) is greater than the gradient dh/db of a second section ( 11 ) of the at least one blade-section side face ( 5, 6 ). The second section ( 11 ) is closer to the base section ( 1 ) than the first section ( 10 ). The sign of the gradients dh/db is the same. In a region which extends to a vertical distance of at most ⅛ of the overall height of the blade section beneath the at least one second portion ( 11 ), there no protrusions or indentations cause a gradient sign change on the at least one blade-section side face ( 5, 6 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is the national phase of PCT/EP2015/055057 filedMar. 11, 2015, which claims the benefit of European Patent ApplicationNo. 14159263.4 filed Mar. 12, 2014.

TECHNICAL FIELD

The invention relates to a sawtooth wire for a roll of a cardingmachine.

BACKGROUND

Carding machines are used to open (individualize) and align fibres of afibrous material, e.g. of wool, cotton, synthetic fibres or of a fibreblend, to homogenize them (for fleece production) and/or to parallelizethem (for yarn production). The carding process may be used to produce afibre mat from a fibrous material. The fibre mat consists of a loosecollection of ordered individual fibres. A nonwoven, for example, may beproduced from a fiber mat of this kind. During carding, the fibre mat isformed by removing the fibres, by way of a removal means, from a largecarding roll known as the swift and combining them.

The carding machine may have various carding rolls, each of which hasteeth, serrations or spikes projecting outwards in approximately radialdirection. The number and/or size and/or density of the teeth,serrations or spikes, as well as their shape and configuration, mayvary.

Carding rolls are generally provided with all-steel card clothing. Thisconsists of a profiled sawtooth wire wound under tension onto thecarding roll in question. The sawtooth wire has a foot segment and ablade segment. The foot segment may have, for example, a rectangular orsquare cross section. In the operating position, the blade segmentprojects away from the foot segment at approx. right angles to thecurved surface of the carding roll. The blade segment has a sawtoothprofile for the formation of teeth or serrations. The sawtooth wire iswound, under longitudinal stress, around the curved surface of thecarding roll, and the two ends are attached to the carding roll.Sawtooth wires are known per se. For example, CN 201512617 U describes asawtooth wire with obliquely slanting teeth on the blade segment.

In U.S. Pat. No. 5,096,506 A, a sawtooth wire is shown where one side ofthe blade segment (blade-segment lateral surface) is perpendicular to,and the other blade-segment lateral surface is inclined relative to thebase area of the foot segment. The inclined blade-segment lateralsurface is flatter on the side further away from the foot segment thanon the rest of the surface. Accordingly, the thickness of the bladesegment increases faster on the side further away from the foot segmentthan in the remaining area of the blade segment.

U.S. Pat. No. 6,185,789 B1, EP 1 408 142 A1 and EP 2 567 010 A1 showsawtooth wires having blade-segment lateral surfaces with a plurality ofconvexities. One of the advantages listed for these sawtooth wires isthat, during the carding process, they are better able to separatenon-spinnable fibres and other foreign substances from the spinnablefibres than are conventional sawtooth wires.

In DE 19 44 251 U and WO 2006/136480 A1, a sawtooth wire is describedwhose one blade-segment lateral surface has a first, upper area that isvery steep. A second planar area adjoins this first portion and isconsiderably flatter than the first area. The transition between thefirst and second areas is at a height much less than half the height ofthe blade-segment lateral surface.

In practice, it has been found that especially the tips of the teeth aresubject to severe wear. Since the tips of the teeth become rounded withtime, the quality and efficiency of the carding process decrease. Acountermeasure consists in regrinding the carding wires mounted on adrum (carding roll). Rounded teeth tips may be resharpened in this way.

However, the latter measure, too, is only able to slow down, but notstop, the long-term loss in quality and efficiency.

SUMMARY

For the reasons cited, the objective of this invention is to create asawtooth wire which enables optimal homogenization and parallelizationof the fibres over a lengthy operating period during production of thefibre mat. The fibres must sustain no or only negligible damage duringthe carding process.

Either staple-fibre yarns or nonwovens may be formed from staple-fibrefleeces.

Among the characteristics of sawtooth wires according to the inventionare foot segments, which serve for seating the wire on a carding roll.The foot-segment surface in contact with the carding roll (when thesawtooth wire has been wound onto it) is referred to as the base area.As a rule, the foot segment is the widest segment of the wire. When thewire has been wound on the carding roll, the lateral edges of the footsegments of adjacent wires usually touch each other.

The base area of the foot segment extends in the wire's longitudinaldirection Z (first spatial direction: is defined by the sawtooth wire'slongitudinal extension) and in the lateral direction B (second spatialdirection: is perpendicular to the wire's longitudinal direction). Thethird spatial direction is the height direction H, which isperpendicular to the base area of the foot segments and extends towardsthe exterior surface of the sawtooth wire (i.e. towards the side of theblade segment facing away from the foot segment). Measured from the basearea, the height values (i.e. the values in the direction of the height)increase to a maximum blade-segment height. Accordingly, the (height)position of points close to the base area is referred to as being “down”and the position of points close to the exterior surface (of thesawtooth wire) as being “up”.

The longitudinal, height and lateral directions of the wire are(pairwise) mutually perpendicular. The three directions thus define aCartesian coordinate system.

The blade segment running in the height direction tapers as a ruletowards the top, i.e. the breadth of the blade segment often decreasessteadily with increasing height. The blade segment is confined in thelateral direction by a first and a second blade-segment lateral surface.One of the two blade-segment lateral surfaces frequently (but notalways) has a gradient dh(b)/db (henceforth: dh/db) of height as afunction of breadth, the value of which is infinitely large, i.e. theblade-segment lateral surface in question is parallel to theperpendicular dropped to the base area of the foot segment. If this isthe case, the aforementioned taper is effected in that the otherblade-segment lateral surface (in the language of this publication “atleast one blade-segment lateral surface”) has a finite gradient dh/db,i.e. the angle between it and the aforementioned perpendicular is not0°.

The height value at which the blade segment has its greatest reach inthe height direction is referred to as the blade segment's maximumheight. The height value at which the blade segment begins (at thebottom thereof) is referred to as the minimum height. The span (in theheight direction) between the minimum height and the maximum height isthe overall height of the blade segment. The minimum and maximum heightsare thus individual height values. The overall height is a distance (alength) in the height direction.

The manufacture of the sawtooth wire commences with the drawing of awire. The wire is subsequently rolled, during which process a wire witha broad foot area and a less broad blade area is formed. The crosssection of the wire is constant, within the manufacturing tolerances,over its length. In the blade-area parts further away from the base areait is customary to periodically punch out recesses, thereby formingteeth. At least the toothed part of the blade area is hardened. Usually,therefore, at least the toothed part of the blade area is of greaterhardness (is harder) than the foot area (this is softer). Sawtooth wirestypically have a length of several hundred metres to several kilometres.

When a sawtooth wire has been wound onto the carding roll, the footsegments form a closed area (except for the narrow gaps between thesawtooth wires). Above the foot segments, carding gaps, as they termed,are formed between adjacent blade segments (the latter being thinnerthan the foot segments). As the blade segments (usually) taper towardsthe top, the carding gaps bordered by the blade segments accordinglywiden steadily towards the top.

The foot area may have planar lateral surfaces. Each foot area may,however, have (profiled) elevations and/or recesses on one lateralsurface and be provided, on the other lateral surface, with inverse(geometrically corresponding) elevations and/or recesses which, when thesawtooth wire is wound onto a carding roll, engage the lateral surfaceof the adjacent wire segment (i.e. the wire segments areinterlinked/interlocked).

The foot segment is clearly distinguishable from the blade segment,since, firstly, it has a geometry (greater breadth) that enables theformation of a (largely) closed area when a sawtooth wire is wound ontoa roll. By contrast, the geometry of the blade segment is such that(when a sawtooth wire has been wound onto a roll) open carding gaps areformed, i.e. the blade segments are always less broad than than theassociated foot segments. Secondly, the blade segments have teeth (i.e.the blade segments end with a serrated outer contour in the heightdirection), whereas foot segments always end, in respect of height, witha largely planar base area. Thirdly, the blade segments are usually (atleast partly) hardened (i.e. they are comparatively hard), whereas thefoot segments are less hard.

In the case of the sawtooth wire according to the invention, theabsolute value of the gradient dh/db at least of a first portion atleast of one blade-segment lateral surface is greater than the absolutevalue of the gradient dh/db at least of a second portion of the sameblade-segment lateral surface.

All the height values of the at least one second portion are smallerthan all the height values of the at least one first portion, i.e. theat least one second portion is below the at least one first portion. Thetwo portions do not overlap.

The at least one first portion and the at least one second portion eachextend between a smallest height value, which is at the bottom of theportion in question, and a maximum height value, which is at the top ofthe portion in question.

The algebraic signs of the gradient dh/db of the at least one first andof the at least one second portion are the same. In other words, a firstportion (at least of one blade-segment lateral surface), which islocated higher up, is steeper relative to the base area of the sawtoothwire (i.e the gradient of this portion is steeper) than is a portion ofthe same blade-segment lateral surface located further down. Bothportions should either rise or fall (i.e. the gradient sign should bethe same for both portions). Whether both portions rise or fall dependson which of the two blade-segment lateral surfaces they are located on.

According to the invention, the gradients dh/db of those portions on thesame blade-segment lateral surfaceside whose height values are in arange extending between the smallest height value of the at least onesecond portion and a further height value which is, at the most, ⅛ ofthe overall height of the blade segment below the aforementionedsmallest height value of the at least one second portion, have the samesign as the gradients dh/db of the at least one first and of the atleast one second portion.

In other words, there should be no elevations (“humps”) or indentations(“dents”) beneath the lower end of the second portion that cause achange in the sign of the gradient. A change in gradient sign should byall means be ruled out within an height range (below the at least onesecond portion) whose height dimension is ⅛ of the blade segment'soverall height. Preferably, the height range in question is ⅕ of theblade segment's overall height. It is also possible to rule out gradientchanges (elevations or indentations) over the entire area of therespective blade-segment lateral surface which is beneath the lower endof the at least one second portion. A further valuable refinement of theinvention may consist in that the gradient dh/db of the at least oneblade-segment lateral surface also has the same sign everywhere abovethe at least one first portion (i.e. above the highest height value ofthe first portion). Alternatively or in addition, provided that thefirst portion does not border directly on the second portion, thegradient dh/db of the at least one blade-segment lateral surface in thearea between the at least one first and the at least one second portion(i.e between the smallest height value of the at least one first portionand the highest height value of the at least one second portion) has thesame sign everywhere.

Elevations/indentations in the flat, rounded transition area between the(comparatively steep) blade segment and the foot segment are irrelevant.Consequently, the term “blade segment” always refers exclusively to therelatively steep area of the blade segment (and not to the flattransition area).

Changes in gradient sign can also be ignored if they are caused by verysmall elevations or indentation attributable to manufacturinginaccuracies or manufacturing flaws.

During the carding process, elevations (indentations) which are sizableand accordingly not attributable to manufacturing flaws/manufacturingtolerances can prevent the fibres from penetrating (in the case ofelevations) or penetrating deeper (in the case of indentations) into thecarding gaps, thereby impairing the process efficiency.

If the elevations/indentations have narrow radii or even sharp edges,they can cause substantial damage to the fibres. Such damage leads toquality shortcomings in the end product (e.g. yarns or fleeces) and mustby all means be prevented.

Since, in the case of the sawtooth wire according to the invention, theat least one first portion located further up on the at least one bladesegment is steeper (steeper gradient dh/db) and the at least one secondportion is flatter (flatter gradient dh/db), the fibres to be carded canenter the carding gaps more easily than with conventional sawtooth wires(whose blade-segment lateral surfaces customarily have a constantgradient). At the level of the smallest height value of the at least onesecond portion, the carding gaps are usually already very narrow, inparticular, substantially narrower than in the height area of theblade-segment lateral surface just beneath its maximum height.Accordingly, elevations/indentations that directly adjoin the at leastone second portion or lie only slightly below this very often causeserious damage to the fibres being carded (on account of the narrowcarding gap), and usually prevent them from penetrating further into thecarding gaps.

Surprisingly, it was found that elevations/indentations located at agreater height distance (typically at least ⅛ of the blade segment'soverall height) below the at least one second portion cause eithernegligible or no damage to the fibres being carded. It is, furthermore,no longer necessary for the fibres to enter further into the respectivecarding gap at this point; i.e. even if the elevations/indentations wereto prevent further penetration of the fibres there, this would havepractically no influence on the carding process.

Elevations/indentations located above the at least one first portion orbetween the at least one first and the at least one second portion causeno or only negligible damage to the fibres being carded and do notprevent these fibres from penetrating the carding gaps because they arein an height area in which the the carding gaps are comparatively wide.

It is advantageous to select precisely the upper end of theblade-segment lateral surface, i.e. the point on the blade-segmentlateral surface whose height corresponds to the maximum height of theblade segment, as the maximum height of the at least one first portion.Alternatively, it is also possible to select a point which (in theheight direction) lies slightly below the upper end, e.g. at the most0.2 (preferably at the most 0.1 mm) below the upper end of theblade-segment lateral surface. Or else a point in the upper quarter,preferably in the upper tenth, of the respective blade-segment lateralsurface is selected as the maximum height of the at least one firstportion. The smallest height value of the at least one first portion isin an area which is 50% to 98%, advantageously 60 to 90%, of the (bladesection's) overall height above the blade section's minimum height.

The at least one first portion is usually positioned longitudinally at apoint on the blade-segment lateral surface at which the height (reach inheight direction) of the latter is comparatively great. It isadvantageous to select, for the at least one first portion, alongitudinal position at which a tooth tip is located.

For the smallest height value of the at least one second portion, aposition is preferably selected in the lower part of the blade segment(nearer the foot segment), e.g. in the bottom tenth of the bladesegment. It suffices, however, if the greatest height value of the atleast one second portion is less than the smallest height value of theat least one first portion. In a preferred variant, the smallest heightvalue of the at least one first portion borders on the greatest heightvalue of the at least one second portion.

In the longitudinal direction, a position for the at least one secondportion is selected at which the sawtooth wire is existent, i.e. not aposition at which the sawtooth wire has a recess (due to the punchingout of teeth).

It should always be assumed that the sawtooth wire runs longitudinally.In particular, the sawtooth wire should not have any deformations in theplane defined by the longitudinal and the lateral directions which couldlead to parts of the blade-segment lateral surface being considered ascurved which are planar in the case of a longitudinally straightsawtooth wire.

The at least one first and the at least one second portion arepreferably selected such that they are on planar parts of the at leastone blade-segment lateral surface. The two portions then run straight inthe plane defined by the height and the lateral directions, i.e. thegradient dh/db is constant in each of the two portions and correspondsin each case to the gradient of the secant which runs in the planedefined by the height and lateral directions and through the at leastone first or the at least one second portion.

The at least one blade-segment lateral surface may, however, also becurved in such a way as to preclude the presence, on the blade-segmentlateral surface in question, of at least one first and/or at least onesecond portion located at a “suitable” height (at a height betweensuitable height values). What is considered as a suitable height hasalready been explained in earlier sections dealing with the heightposition of the at least one first and the at least one second portion.

In a case of this kind, the at least one first portion and/or the atleast one second portion may be infinitesimally small (especially in theheight direction), i.e. in the case of the infinitesimally small portionconcerned, the gradient can no longer be determined in a finitestraight/planar portion but at a point. To persons skilled in the art,this situation is known from the introduction to differential calculus,since here the differential quotient for the limit value observation ofinfinitesimally close arguments (here breadth values) expresses thegradient at a point:

${\lim\limits_{{\Delta \; b}arrow 0}\frac{\Delta \; h}{\Delta \; b}} = \frac{h}{b}$

For this case (infinitesimal portion breadth), the tangent is a specialcase of the secant through a planar portion, and the value of the secantgradient is the value of the derivative of the function describing thecourse of the contour of the blade segment in question, or, expressedmore simply, the value of the gradient at this point.

The two portions may (but need not) lie one above the other in theheight direction. If one were able to use the starting profile for thesesawtooth wires, i.e. the original shape of the sawtooth wire prior tothe generation of teeth (e.g. by punching or by a method producing thesame effect) as a basis, it would be easy to select the two portionssuch that they are disposed one above the other in respect of height.However, sawtooth wire teeth are often oblique, i.e. they are shapedlike the teeth of a saw, which slope. When determining the tooth's angleof slope, it is customary to use the slope of the tooth face (workingangle). The working angle is defined as the angle enclosed between thetooth face and the perpendicular. On account of the tooth's slope, manysawtooth wires have no position at which a complete and gaplesscross-section (through the original profile) can be found. It is thennecessary not to arrange the portions one above the other in respect ofheight (i.e. the two portions lie at different points of the sawtoothwire's longitudinal reach).

A length of 1/100 mm may be preferable as minimum length of the portions(in the lateral direction), although a length of 5/100 or 1/10 mm mayalso be to advantage.

The other blade-segment lateral surface (the blade-segment lateralsurface opposite the at least one blade-segment lateral surface) ispreferably almost completely in a plane defined by the height andlongitudinal directions, i.e. its gradient dh/db is infinite. It may,however, have a different geometry, e.g. it could be inclined relativeto the height direction by a small angle, e.g. of less than 3° (i.e. itsgradient dh/db may have a finite value). Or it could be mirror-symmetricto the at least one blade-segment lateral surface.

In the case of customarily used sawtooth wires (or in the case of theirstarting profiles), both blade-segment lateral surfaces (with theexception of curved transition areas) are virtually completely planar,with one blade-segment lateral surface extending in a plane defined bythe height and longitudinal directions and the second blade-segmentlateral surface extending (likewise in the longitudinal direction but)inclined in respect of height. With sawtooth wires of this kind, thebreadth (lateral spread) of the sawtooth wire increases linearly overthe entire blade segment.

By virtue of the blade-segment geometry (of the at least oneblade-segment lateral surface) proposed in the invention, the breadth ofthe blade segment increases more slowly (or not at all) in the upperarea (farther away from the foot segment) and then, in the lower area,increases more rapidly (than in the upper area). The transition betweenthe small (or non-existent) increase in breadth and the strongerincrease may be continuous or take place in one or more steps, e.g. byway of a succession of several planar portions, e.g. a maximum of 4,preferably 2 to 3. The technical implementation of each of thesevariants will be explained in more detail below.

The breadth of the carding gaps formed by a sawtooth wire according tothe invention and mounted on a carding roll accordingly decreases—withdecreasing height—less quickly (or not at all) in the upper area (nearerthe teeth of the sawtooth wire) of the carding gaps, and more quickly inthe lower area.

Surprisingly, it was found that when the sawtooth wire according to theinvention is used, the loss in quality and efficiency of the cardingprocess over time (due mainly to necessary regrinding of the teeth) issignificantly less than is the case with conventional wires. Thesawtooth wire of the invention thus enables optimal homogenization andparallelization of the fibres (during the production of a fibre mat)over a lengthy operating period.

The sawtooth wire usually has an exterior surface which bounds thesawtooth wire (in the height direction) on the side facing away from thefoot segment, and which also extends in the height direction. In sodoing, it (often) defines at least one tooth (usually many teeth) of thesawtooth wire. In other words, the blade-segment lateral surface has aserrated contour, at least in its upper area.

At the tip of the at least one tooth, the exterior surface extendssubstantially in the longitudinal direction (Z) and the lateraldirection (B). The exterior surface of the tooth flanks, by contrast, isinclined in respect of height.

In one embodiment of the invention, the two portions of the at least onetooth are typically arranged such that they are longitudinallystaggered. In this way it is ensured that each of the two portions islocated at a point of the sawtooth wire where no material has beenremoved (by punching during tooth production). This arrangement makes itpossible to locate the topmost portion at or near the tip of the atleast one tooth and, simultaneously, to locate the at least one secondportion at the lower end, or at least in the vicinity of the lower end,of the blade segment (in the area of the respective tooth). The entire(or almost the entire) height of the blade segment can hereby beencompassed by the two portions.

Arranging the two portions such that are longitudinally staggered, asdescribed above, is unproblematic because sawtooth wires are made fromprofiled wires the cross-sectional profile of which remains practicallythe same over their length.

In principle, the at least one first and the at least one second portionmay also be located at a single longitudinal position of the sawtoothwire, i.e. they are arranged one above the other in the heightdirection, as described above. This is possible in cases where no hollow(punched out) areas exist beneath the tooth tip in question, i.e. if theline connecting the (at least one) first and the (at least one) secondportion runs completely within the sawtooth-wire material.

In a preferred embodiment, at least the part of the blade-segmentlateral surface reaching from the blade segment's maximum height to apoint which is 2%, preferably 5% or, best of all, 10% of the bladesegment's overall height above the minimum height of the blade-segmentlateral surface is made up of at least two planar surface portions.Expressed differently, the at least one blade-segment lateral surface(of the sawtooth wire) has at least two planar surface portions, whichextend straight in the plane defined by the lateral and heightdirections. The two surface portions preferably follow each other insuccession (adjoin each other) in the height direction and enclose anangle (which does not equal 0°) in the plane defined by the lateral andheight directions.

It is also possible for more than two planar (straight) surface portionsto follow each other in succession in the height direction, e.g. threeor four straight surface portions. Two or three planar surface portionsare preferred. The planar surface portion furthest from the foot segment(the highest surface portion) and the second surface portion borderingthereon (the one nearer the foot segment) preferably adjoin each otherat a height in the range between 5/10 and 9/10, preferably ⅖ and ⅘ ofthe blade segment's overall height.

The invention is particularly advantageous for (fine) sawtooth wireswith comparatively low blade segments, i.e with heights of the bladesegments (alternatively: of the teeth) ranging from 0.3 to 1 mm.Sawtooth wires of this kind are customarily used for the manufacture ofstaple-fibre yarns, e.g. of cotton and/or synthetic fibres.

For coarser fibres, sawtooth wires are used that may have blade segmentswith a height of up to 3 (in exceptional cases up to 4) mm.

In the case of fine sawtooth wires it is to advantage that the portionfurthest away from the foot segment (the at least one first portion)usually has a height (reach in h direction) of 0.1 to 0.5 mm, preferablyof 0.2 to 0.3 mm. This preferred planar portion preferably begins at amaximum distance of 5/100 mm or 1/10 mm below the tooth tip, i.e. theupper height value of the at least one first portion is, at the most,5/100 or 1/10 mm smaller than the blade segment's maximum (height)value.

If the aforementioned ranges are selected, carding quality andefficiency losses due to necessary regrinding of the teeth of thesawtooth wire are significantly less than is the case when conventionalwires are used.

In order to prevent sawtooth wires, i.e. the gaps formed by sawtoothwires, from becoming blocked with fibres (when the wires are in serviceon a carding roll), at least in a sufficiently large area of thesawtooth-wire the blade segments must taper sufficiently fast in theheight direction. Conventional sawtooth wires practically always fulfillthis requirement. However, if the area in which the breadth of thesawtooth wire according to the invention only increases slightly or notat all (small angle of slope relative to the height direction) were toextend over the entire blade-segment lateral surface concerned, blockingof the gaps would have to be anticipated. Via suitable selection of therespective height range, the sawtooth wires are prevented from becomingblocked with fibres despite the (at least first) blade-segment lateralsurface being very steep in part (correlating with little-pronouncedtapering of the blade segment).

The at least one first portion (the portion in which the breadth of thesawtooth wire increases less) of the at least one blade-segment lateralsurface usually makes an angle of less than 5°, preferably 0°-2°, withthe perpendicular dropped to the base area of the foot. Accordingly,since 0° are also possible, the (at least one) first portion of the (atleast one) blade-segment lateral surface may also be parallel to theperpendicular dropped to the base area of the foot.

The at least one second portion of the at least one blade-segmentlateral surface usually makes an angle of more than 6°, preferably,however, of more than 8°, with the perpendicular dropped to the basearea of the foot. This angle is typically less than 15°, preferably lessthan 12°.

In an alternative embodiment, the portions of the at least oneblade-segment lateral surface may extend curvilinearly in the planedefined by the lateral and height directions. In particular, the entireblade-segment lateral surface may be curved, preferably concave (as seenfrom the exterior). Curved means the absence of kinks in the portionconcerned. Kinks are points at which discontinuities or singular pointsoccur in the gradient (of the portion concerned).

Ultimately, variants are also conceivable in which the at least oneblade-segment lateral surface is formed from a combination of curvedsurface portions and planar surface portions.

In this embodiment (curved surface portions), too, it is possible tomaintain comparatively high efficiency of the carding process for longerthan is possible when conventional sawtooth wires are used. At the sametime, it is also possible to prevent the carding gaps formed by thesawtooth wires from becoming blocked with fibres. For this purpose (byanalogy with the embodiment having planar portions), a height in therange between 5/10 and 9/10, preferably ⅗ and ⅘, of the blade segment'smaximum height is selected for the point at which the surface portion inwhich the breadth of the sawtooth wire increases faster and the surfaceportion in which it increases more slowly border on one another. If theentire blade-segment lateral surface is curved, a suitable limitingvalue (for the maximum breadth increase per unit of height) may bespecified for determination of this point.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below on the basis of threeembodiments. The drawing in

FIG. 1: is a perspective view of a sawtooth wire,

FIG. 2: shows a cross section of a sawtooth wire having a blade-segmentlateral surface with two planar surface portions; for reasons ofclarity, the wire is shown enlarged in the lateral direction.

FIG. 3: shows a profile of a sawtooth wire having a blade-segmentlateral surface with two planar surface portions;

FIG. 4: shows a cross section of a sawtooth wire having a blade-segmentlateral surface with four planar surface portions; for reasons ofclarity, the wire is shown enlarged in the lateral direction.

FIG. 5: shows a profile of a sawtooth wire having a blade-segmentlateral surface with four planar surface portions;

FIG. 6: shows a cross section of a sawtooth wire the blade-segmentlateral surface of which is a concave curve; for reasons of clarity, thewire is shown enlarged in the lateral direction.

FIG. 7: shows a profile of a sawtooth wire with a concave blade-segmentlateral surface;

FIG. 8: shows the determination of contour gradients in the planeextending in the height direction H and lateral direction B;

FIG. 9: shows a blade segment and choice of position for the first andsecond portions on the blade segment;

FIG. 10: shows an alternative shape for the foot segment;

FIG. 11: shows a first shape for the second blade-segment lateralsurface;

FIG. 12: shows a second shape for the second blade-segment lateralsurface;

FIG. 13: shows a further cross section of a sawtooth wire.

DETAILED DESCRIPTION

The section of sawtooth wire shown in FIG. 1 consists of a foot segment1 featuring a base area 2 and two lateral surfaces 3, and a bladesegment 4 which adjoins the foot segment 1 and has a first blade-segmentlateral surface 5 and a second blade-segment lateral surface 6. On theside further away from the foot segment 1 (facing upwards), the bladesegment 4 is delimited by an exterior surface 7, which undulates along aserrated path in such a manner as to form teeth 8.

The sawtooth wire runs in the longitudinal direction Z; its heightextends in the height direction H and its breadth in the lateraldirection B (B is perpendicular to both Z and H).

The height value at which the blade segment 4 has its greatest reach inthe height direction H is referred to as the blade segment's maximumheight h_(max). The height value at which the blade segment begins (atthe bottom thereof) is referred to as the minimum height h_(min). Thespan (in the height direction) between the minimum height h_(min) andthe maximum height h_(max) is the overall height H_(max) of the bladesegment.

The second blade-section lateral surface 6 extends (apart frommanufacturing tolerances) in a plane spanned by the longitudinaldirection Z and the height direction H.

The first blade-segment lateral surface 5 is made up of a first portion10 located higher up on the blade segment 4 (further away from the footsegment 1) and a second portion 11 located lower down on the bladesegment (nearer the foot segment 1). As already explained earlier, thecomparatively flat, rounded transition area 9 between the foot segment 1and the blade segment 4 is not part of the blade segment 4. The firstportion 10 is practically parallel to the plane defined by thelongitudinal direction Z and the height direction H (accordingly, it isalso parallel to the second blade-segment lateral surface 6), i.e. itsgradient is infinitely large. The first portion 10 may alternativelyenclose a small angle not exceeding 2° with the height direction H (i.e.dh/db assumes a finite value) and, except for manufacturing tolerances,run parallel to the longitudinal direction Z.

The second portion 11 is also parallel to the longitudinal direction Z(except for manufacturing tolerances) but, compared with the firstportion 10, encloses a substantially larger angle of 8° to 12° with theheight direction H. In other words, the first portion 10 is steeper thanthe second portion 11. A steep run generally means that dh/db is large.For a flat run, dh/db is accordingly small.

On account of the particular geometry of the blade-segment 4, itsbreadth B initially increases very slowly (or not at all) from the topdownwards, e.g. starting from one of the tooth tips 12 (technicallyspeaking, the tip is a short edge), as its height decreases (i.e.towards the foot segment). At the transition 13, at which the firstportion 10 merges into the second portion 11, the breadth of the bladesegment 4 then increases faster (or commences to increase) withdecreasing height. The sawtooth wire's property of featuring a bladesegment 4 the breadth of which, starting from the top, initiallyincreases more slowly and then, towards the bottom, increases morequickly, is essential to the invention and is shown by a multiplicity ofadvantageous embodiments thereof. Of course, this applies only to thoseareas of the sawtooth wire in which the material of the original profileis still there, i.e. in which no material was punched out.

In FIG. 2 the cross section of the sawtooth wire shown in FIG. 1 isillustrated, and in FIG. 3 the associated starting profile(corresponding to the sawtooth wire without teeth). The sectional plane(of the cross section) extends in the lateral direction B and the heightdirection H. In FIG. 2—as in FIGS. 4 and 6—the lateral direction B isshown enlarged (i.e. the overall breadth B_(max) of the sawtooth wire isshown enlarged compared to the overall height H_(max),) in order toenable the viewer to recognize the angles and gradients.

As is apparent from FIG. 2, the first portion 10 (in the respectivesectional plane) is delimited by the end points 14 and 15 and the secondportion 11 by the end points 15 and 16. The first secant 17, which runsalong the first portion 10 (i.e. through the end points 14, 15 of thefirst portion 10) in the sectional plane defined by the lateraldirection B and the height direction H, has a steeper gradient than thesecond secant 18, which runs in the same plane and along the secondportion 11 (through the end points 15, 16 of the second portion).

FIG. 4 shows the cross section (and FIG. 5 the associated profile) of asawtooth wire the first blade-segment lateral surface 5 of which is madeup of four planar surface portions following each other in succession inthe height direction H. The uppermost planar surface portion (furthestfrom the foot segment 1), which (in this sectional plane) is delimitedby the end points 20 (with the height value h₁₁) and 21 (with the heightvalue h₁₂), has been selected here as the first portion 10. The seconduppermost planar surface portion, which is delimited by the end points23 (with the height value h₂₁) and 24 (with the height value h₂₂) hasbeen selected as the second portion 11. The first secant 22 runs throughthe end points 20 and 21, the second secant 25 through the end points 23and 24. Both secants 22, 25 run in the plane defined by the lateraldirection B and the height direction H. Here too, the secant 22 has asteeper gradient than the secant 25, i.e. the secant 22 encloses asmaller angle α1 with the perpendicular 19 dropped to the base area 2 ofthe foot segment than does the secant 25 (angle α2).

Beneath the end point 24, with the height value h₂₂ of the at least onesecond portion, is the further height value h₃. The further height valueh₃ is located (at a distance in the height direction H) approximately ⅛of the overall height H_(max) beneath the lower height value h₂₂ of theat least one second portion. No change in the sign of the gradient dh/dbis allowed in the area between these two height values, i.e. noelevations or indentations are allowed in this area.

FIG. 6 shows the cross section (and FIG. 7 the associated profile) of asawtooth wire the first blade-segment lateral surface 5 of which (seenfrom the outside) is a concave curve (with no kinks). In FIG. 6—asbefore in FIGS. 2 and 4—the lateral direction B is once again shownenlarged so that the viewer is able to recognize different anglesbetween the perpendicular 19 and the tangents 27 and 30. It remains tobe mentioned that in FIGS. 2, 4 and 6 the points 14, 15, 16, 20, 21, 23,24, 26 and 29 are represented by horizontal strokes, which intersect thecontour of the sawtooth wire 1. The respective point lies at theintersection between the horizontal stroke and the contour of thesawtooth wire 1.

An infinitesimally small surface portion 26 in the height direction H(punctiform relative to the selected sectional plane) has been selectedas the first portion 10. Here, the tangent 27 to the first blade-segmentlateral surface 5 at the surface portion/point 26 takes the place of theotherwise customary secant running along a planar portion (in the planedefined by the lateral and height directions). The second portion 11 isformed analogously by the point 29, with the tangent 30 in place of thesecant along a planar portion. Here too (as with the respective secants)the gradients of the tangents correspond in each case to the derivativedh/db at the respective point. As in the two preceding examples, thetangent 27 has a steeper gradient dh/db than the tangent 30, i.e. thetangent 27 encloses a smaller angle α1 with the perpendicular 19 droppedto the base area 2 of the foot segment than does the tangent 30 (angleα2).

FIG. 8 shows the contours of two first blade-segment lateral surfaces 5in the plane defined by the height direction H and the lateral directionB. The one first blade-segment lateral surface 5 running in therespective plane is entirely curved 31, the other first blade-segmentlateral surface 32 is made up of two planar surface portions 33, 34. Thelateral direction B is again shown in enlarged form.

In the case of the blade-segment lateral surface 32, which comprises twoplanar surface portions, the first portion 10 may be selected as thesurface portion 33, which extends between the points with thecoordinates (b₁₁, h₁₁) and (b₁₂, h₁₂), and the second portion 11 as thesurface portion 34, which extends between the points with thecoordinates (b₂₁, h₂₁) and (b₂₂, h₂₂). The gradient of the secantthrough the end points of the first portion 10 is then(h₁₂-h₁₁)/(b₁₂-b₁₁), the gradient of the secant through the end pointsof the second portion 11 is (h₂₂-h₂₁)/(b₂₂-b₂₁).

For the blade-segment lateral surface 31, which is entirely curved, thefirst portion 10 and the second portion 11 are selected (at least in theviewing plane) to be infinitesimally small (i.e. punctiform). Thegradient of the first portion 10 equals the derivative dh/dh at thepoint b₁₁ (or at the point b₁₂, since the two end points of theinfinitesimally small portion 10 coincide), the gradient of the secondportion 11 equals the derivative dh/db at the point b₂₁ (or b₂₂).

FIG. 9 shows a tooth 8 whose height corresponds to the overall heightH_(max) of the blade segment 4, i.e. the overall height of the tooth 8equals the overall height H_(max) (=h_(max)−h_(min)) of the bladesegment 4.

The tooth has, in the area of the tooth tip 12, a first planar surfaceportion 35, which is steeper, and, further down, a second planar surfaceportion 36, which is flatter. The two surface portions 35, 36 border oneach other at the partition line 37.

It is possible to select either a first portion 110 b, which extendsbetween the height values h′11 and h′12, and a second portion 111 (whichextends between the height values h21 and h22), which have the samereach z1 in the longitudinal direction Z. Or it is possible to select afirst portion 110 a, which extends between the height values h11 andh12, and the second portion 111, the two portions 110 a and 111 havingdifferent reaches z1, z2 in the longitudinal direction Z.

As is evident from FIG. 10, the foot segment 1 may be shaped such thatadjacent wire sections interlock (linked configuration). The gradientsof the side walls 38 of the foot segment are not subject matter of thisapplication.

In FIGS. 11 and 12, embodiments of the second blade-segment lateralsurface 6 are illustrated. The second blade-segment lateral surface 6shown in FIG. 11 is approx. mirror-symmetric to the first blade-segmentlateral surface 5. FIG. 12 shows a blade-segment lateral surface 6 whichis slightly inclined relative to the height direction H.

FIG. 13 shows that the at least one blade-segment surface 5 of thesawtooth wire showing the feature essential to the invention may alsolie on the “other” side of the sawtooth wire 1.

LIST OF REFERENCE NUMERALS

-   1 Foot segment-   2 Base area of foot segment-   3 Lateral surface of foot segment-   4 Blade segment-   5 First blade-segment lateral surface-   6 Second blade-surface lateral surface-   7 Exterior surface of blade segment-   8 Tooth-   9 Rounded transition area between blade segment and foot segment-   10 First portion-   11 Second portion-   12 Tooth tip-   13 Transition between first and second portions-   14 First end point-   15 Second end point-   16 Third end point-   17 First secant-   18 Second secant-   19 Perpendicular dropped to the base of the foot-   20 First end point-   21 Second end point-   22 First secant-   23 Third end point-   24 Fourth endpoint-   25 Second secant-   26 Infinitesimally small first surface portion/first point-   27 Tangent to the first surface portion-   29 Infinitesimally small second surface portion/second point-   30 Tangent to the second surface portion-   31 Curved contour of the blade-segment lateral surface-   32 Contour of the blade-segment lateral surface, which is made up of    two planar surface portions-   33 First planar surface portion-   34 Second planar surface portion-   35 Steeper planar surface portion-   36 Flatter planar surface portion-   37 Dividing line between the steeper and the flatter planar surface    portions-   38 Side walls of the foot-   110 a First portion-   110 b First portion (alternative)-   111 Second portion-   Z Longitudinal direction-   B Lateral direction-   H Height direction-   B_(max) Overall breadth of blade segment-   b₁₁ Upper lateral value of first portion-   b₁₂ Lower lateral value of first portion-   b′₁₁ Upper lateral value of first portion (alternative)-   b′₁₂ Lower lateral value of first portion (alternative)-   b₂₁ Upper lateral value of second portion-   b₂₂ Lower lateral value of second portion-   H_(max) Overall height of blade segment-   h_(max) Maximum height of blade segment-   h_(min) Minimum height of blade segment-   h₁₁ Upper height value of first portion-   h₁₂ Lower height value of first portion-   h′₁₁ Upper height value of first portion (alternative)-   h′₁₂ Lower height value of first portion (alternative)-   h₂₁ Upper height value of second portion-   h₂₂ Lower height value of second portion-   h₃ Further height value-   z₁ First longitudinal reach value-   ′z₂ Second longitudinal reach value-   α1 Angle between the first portion and the perpendicular dropped to    the base-   α2 Angle between the second portion and the perpendicular dropped to    the base-   α3 Angle between the first and second portions

1. Sawtooth wire for mounting on a carding roll of a carding machine,the sawtooth wire comprising: a) a foot segment (1) with a base area (2)to be supported on a clothing roller, the base area (2) extending in alongitudinal direction (Z) and a lateral direction (B) of the sawtoothwire, b) a blade segment (4) extending in a height direction (H), whichis perpendicular to the base area (2), and having height values, asmeasured from the base area (2), increasing in a direction of a side ofthe blade segment (4) facing away from the foot segment (1) up to amaximum height (hmax) of the blade segment (4), and c) the blade segment(4) being confined in the lateral direction (B) by a first (5) and asecond (6) blade-segment lateral surface, wherein: d) an absolute valueof a gradient dh/db of height (h) as a function of breadth (b) at leastof a first portion (10) at least of one of the first and the secondblade-segment lateral surface (5, 6) is greater than a absolute value ofa gradient dh/db of at least a second portion (11) of the at least ofone of the first and the second blade-segment lateral surface (5, 6),wherein height values of the at least one second portion being smallerthan height values of the at least one first portion (10) and thegradient dh/db of the at least one first portion (10) and of the atleast one second (11) portion having a same sign, e) gradients dh/db ofportions on a same blade-segment lateral surface (5, 6) whose heightvalues are in a range extending between a smallest height value (h22) ofthe at least one second portion (11) and a further height value (h3)which is located, at most, at ⅛ of an overall height (Hmax) of the bladesegment (4) below the smallest height value (h22) of the at least onesecond portion (11), have the same sign as the gradients dh/db of the atleast one first portion (10) and of the at least one second (11)portion, and f) a smallest height value (h12) of the at least one firstportion (10) being located in an area which is 50% to 98% of the overallheight (Hmax) above a minimum height (hmin) of the blade segment (4). 2.Sawtooth wire according to claim 1, wherein the gradients dh/db of theportions on the same blade-segment lateral surface (5, 6) whose heightvalues are in the range extending between the smallest height value(h22) of the at least one second portion (11) and the further heightvalue (h3) which is, at the most, ⅕ of the overall height (Hmax) of theblade segment below the smallest height value (h22) of the at least onesecond portion (11), have the same sign as the gradients dh/db of the atleast one first portion (10) and of the at least one second (11)portion.
 3. Sawtooth wire according to claim 1, wherein the gradientsdh/db of the portions on the same blade-segment side (5, 6) whose heightvalues are smaller than the smallest height value (h22) of the at leastone second portion (11) have the same sign as the gradients dh/db of theat least one first (10) and of the at least one second (11) portion. 4.Sawtooth wire according to claim 1, wherein the smallest height value(h12) of the at least one first portion (10) borders on a largest heightvalue (h21) of the at least one second portion (11).
 5. Sawtooth wireaccording to claim 1, comprising: an exterior surface (7), which limitsthe sawtooth wire in the height direction (H) on a side facing away fromthe foot segment (1) and which also extends in the height direction (H)and in so doing defines at least one tooth (8) of the sawtooth wire, andwherein the at least one tooth (8) includes the at least one firstportion (10) and the at least one second (11) portion.
 6. Sawtooth wireaccording to claim 1, wherein the at least one first portion (10) andthe at least one second portion (11) are located at a point (z) in thesawtooth wire's longitudinal direction (Z).
 7. Sawtooth wire accordingto claim 1, wherein surface portions of the at least one blade-segmentlateral surface (5, 6), which extend curvilinearly in a plane defined bythe lateral direction (B) and the height direction (H).
 8. Sawtooth wireaccording to claim 1, comprising a first straight surface portion (33)and a second (34) straight surface portion of the at least oneblade-segment lateral surface (5, 6), which extend straight in a planedefined by the lateral direction (B) and the height direction (H), whichfollow each other in succession in the height direction (H), and whichdefine an angle (α3) in the plane defined by the lateral direction (B)and the height direction (H).
 9. Sawtooth wire according to claim 1,wherein at most four straight surface portions follow each other insuccession in the height direction (H).
 10. Sawtooth wire according toclaim 1, wherein a highest straight surface portion (33) and a surfaceportion (34) adjacent thereto border on each other in a height regionlocated between 5/10 and 9/10 of the overall height (Hmax) above theminimum height (hmin) of the blade segment (4).
 11. Sawtooth wireaccording to claim 1, comprising at least a first portion (10) of the atleast one blade-segment lateral surface (5, 6), said first portionmaking an angle of less than 5° with a line perpendicular (19) droppedto the base area (2) of the foot.
 12. Sawtooth wire according to claim11, wherein the at least a first portion (10) of the at least oneblade-segment lateral surface (5, 6) runs parallel to the lineperpendicular (19) to the base area of the foot.
 13. Sawtooth wireaccording to claim 1, comprising at least one first portion (10) of thefirst blade-segment lateral surface (5), said first portion runningparallel to a portion, located at a same height, of the secondblade-segment lateral surface (6).
 14. Sawtooth wire according to claim11, comprising at least a second portion (11) of the at least oneblade-segment lateral surface (5, 6), said second portion making anangle (α2), which is greater than 6°, with the line perpendicular (19)to the base area of the foot.
 15. Method of manufacturing fibre fleeces,the method comprising: processing cotton and/or synthetic fibres using asawtooth wire comprising: a) a foot segment (1) with a base area (2) tobe supported on a clothing roller, the base area (2) extending in alongitudinal direction (Z) and a lateral direction (B) of the sawtoothwire, b) a blade segment (4) extending in a height direction (H), whichis perpendicular to the base area (2), and having height values, asmeasured from the base area (2), increasing in a direction of a side ofthe blade segment (4) facing away from the foot segment (1) up to amaximum height (hmax) of the blade segment (4), and c) the blade segment(4) being confined in the lateral direction (B) by a first (5) and asecond (6) blade-segment lateral surface, wherein: d) an absolute valueof a gradient dh/db of height (h) as a function of breadth (b) at leastof a first portion (10) at least of one of the first and the secondblade-segment lateral surface (5, 6) is greater than a absolute value ofa gradient dh/db of at least a second portion (11) of the at least ofone of the first and the second blade-segment lateral surface (5, 6),wherein height values of the at least one second portion being smallerthan height values of the at least one first portion (10) and thegradient dh/db of the at least one first portion (10) and of the atleast one second (11) portion having a same sign, e) gradients dh/db ofportions on a same blade-segment lateral surface (5, 6) whose heightvalues are in a range extending between a smallest height value (h22) ofthe at least one second portion (11) and a further height value (h3)which is located, at most, at ⅛ of an overall height (Hmax) of the bladesegment (4) below the smallest height value (h22) of the at least onesecond portion (11), have the same sign as the gradients dh/db of the atleast one first portion (10) and of the at least one second (11)portion, and f) a smallest height value (h12) of the at least one firstportion (11) being located in an area which is 50% to 98% of the overallheight (Hmax) above a minimum height (hmin) of the blade segment (4).16. Method according to claim 15, wherein the processing the cottonand/or synthetic fibres using the sawtooth wire comprises processing thecotton and/or synthetic fibres using a sawtooth wire having the overallheight (Hmax) of less than 4.0 mm.
 17. Method according to claim 15,wherein the processing the cotton and/or synthetic fibres using thesawtooth wire comprises processing the cotton and/or synthetic fibresusing a sawtooth wire having a highest straight surface portion (33) anda second surface portion (34) bordering the highest straight surfaceportion (33) in a height region which, in the height direction (H), islocated between 5/100 and 2/10 mm below the maximum height (hmax).